Simulating the effect of glacial sea level changes on Indo-Pacific climate

Thursday, 18 December 2014: 8:15 AM
Pedro N Di Nezio, University of Hawai''i at Manoa, Honolulu, HI, United States, Jessica E Tierney, WHOI, Woods Hole, MA, United States, Axel Timmermann, IPRC, University of Hawaii at Manoa, Honolulu, HI, United States, Bette L Otto-Bliesner, National Center for Atmospheric Research, Boulder, CO, United States and Brian E Mapes, RSMAS, University of Miami, Atmospheric Sciences, Miami, FL, United States
Lowered sea level during the Last Glacial Maximum (LGM) altered the geography of the Maritime Continent exposing the Sunda shelf. Multi-proxy evidence indicates that the exposure of the Sunda shelf has a first-order effect on the climate of the Indo-Pacific warm pool. The climate response involves changes in the Walker circulation driven by a massive reduction in atmospheric deep convection over the Sunda shelf. Few climate models participating in the Paleo Model Intercomparison Project (PMIP) are capable of simulating this response. Using the Community Earth System Model Version 1 (CESM1) we show that a models ability of to simulate this response depends on the formulation of the atmospheric deep convection scheme. Using CESM1 we also find that the Indian Ocean amplifies the response via the Bjerknes feedback. This results in a large reorganization of the climate of the Indian Ocean, which during the LGM resembles the Pacific, with a cold tongue and dry conditions in the east, and warmer SSTs and wetter conditions in the west. Ideas for testing these mechanisms using proxy data will be discussed.